Open Stack

John,


The main point here is to reduce amount of data that we request from DB and
that is process by API services and sent via network
and make SQL requests simpler (remove joins from SELECT).

So like if you fetch 10 bytes instead of 1000 bytes you will process 100
times less and it will scale 100 timer better and work overall 100 time
faster.

>From other side polling may easily cause 100 API requests / second And
create significant load on the cloud.

Clint,

Please do not forget abut the fact that we are removing from SQL requests
JOINs.

Here is how look SQL request that gets VM info:
http://paste.openstack.org/show/477934/ (it has 6 joins)

This is how it looks for glance image:
http://paste.openstack.org/show/477933/ (it has 2 joins)

So the performance/scale impact will be higher.

Best regards,
Boris Pavlovic


On Wed, Nov 4, 2015 at 4:18 PM, Clint Byrum <clint at fewbar.com> wrote:

> Excerpts from Boris Pavlovic's message of 2015-11-03 17:32:43 -0800:
> > Clint, Morgan,
> >
> > I totally agree that the pub/sub model is better approach.
> >
> > However, there are 2 great things about polling:
> > 1) it's simpler to use than pub/sub (especially in shell)
>
> I envision something like this:
>
>
> while changes=$(openstack compute server-events --run react-to-status
> --fields status id1 id2 id3 id4) ; do
>   for id_and_status in $changes ; do
>     id=${id_and_status##:}
>     status=${id_and_status%%:}
>   done
> done
>
> Not exactly "hard"
>
> > 2) it has really simple implementation & we can get this in OpenStack in
> > few days/weeks
> >
>
> It doesn't actually solve a ton of things though. Even if we optimize
> it down to the fewest operations, it is still ultimately a DB query and
> extra churn in the API service.
>
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